That's a sg feature ;)
Even your name changes color in your giveaways, just watch carefully :)

I don't exactly remember how it works but it takes the color from the game image on the left; however, the main color? the mean of all colors? I don't remember, sorry :\

Still, if noone else shows up to exactly tell you how does it work, I think this can suffice :) still better than nothing =P

Enjoy!